This invention relates to the production of olefin polymers by polymerization with a magnesium alkoxide polymerization catalyst. More particularly, the present invention relates to the improvement of the morphology, and sometimes productivity, of polmerization catalysts formed from magnesium alkoxides having alcohol solvate.
Experience has shown that the best magnesium chloride supported titanium tetrahalide catalysts for olefin polymerization are prepared via metathesis of a suitable magnesium compound rather than forceful mechanical and chemical treatment of magnesium chloride. Very good commercial polymerization catalysts have been prepared via metathesis of magnesium alkoxide using titanium tetrachloride in the presence of an ester and, optionally, a halohydrocarbon as disclosed in U.S. Pat. Nos. 4,400,302 and 4,414,132. Many of these magnesium alkoxides have bound alcohol (alcohol solvate) which I believe should be removed in order to make a good catalyst. For instance, magnesium methoxide does not metathesize well because, as the initially formed solvate methanol is thermally removed, it may catalyze the polymerization to the intractable [Mg(OMe).sub.2 ].sub.n species. When bound alcohol is removed from magnesium alkoxides in a haphazard fashion such as by heating in an inert atmosphere, the resulting catalyst generally exhibits inferior morphology. It is an object of the present invention to provide a method for removing the bound alcohol from magnesium alkoxides which allows the production of a catalyst with superior morphology.